The present invention relates to a device for separating and depositing individual grains, particularly seeds, under utilization of a funnel and an air flow by means of which all but one pieces of grain are blown out of the funnel, and subsequently, the lower portion of the funnel is opened, permitting the single piece of grain to fall out.
My copending patent application, Ser. No. 088,866, filed on Oct. 29, 1979, discloses a device for that purpose, in which the lower portion of the funnel is constructed as a pair of brackets, defining the funnel-shaped chamber with a narrow duct opening that is too small to permit a single piece of grain to fall through.
Upon opening the funnel by pivoting at least one of the bracket elements, the duct is widened temporarily, and that one particular piece of grain can now fall out. The aerodynamics of the system is such that, with closed brackets and a narrow duct opening only one piece of grain can, indeed, be retained in the bottom of the funnel while all others are blown out and retained in a hovering state by the introduction of an air current. The principle of operation, as far as the singling out and separating one grain from the others is concerned, results from the fact that the bottom duct of the funnel is partially, but not completely, closed by one piece of grain; and upon blowing air into the funnel, a certain venturi effect takes place around the surface of that one piece of grain, causing a low pressure to surround same and sucking it thereby, in effect, against the funnel wall adjacent to the duct. On the other hand, no such retension force is available to the other pieces of grain, which are, in effect, blown out by the airflow. In particular, not all of the air being blown into the funnel escapes through the duct, but a sizable portion is deflected and flows up again; and the other pieces of grain are, aerodynamically forced to follow that flow.
The operation of such a device is highly dissatisfactory and the retension of a single piece of grain as well as its separation from other grains is a consistently and reliably carried-out operation. The pieces of grain, being carried upward by the airflow, will, of course, begin to fall when the brackets are opened. Speedy reclosing of the brackets is required so that, when the lowest-most of the falling grains has dropped by a significant distance, the bracket and funnel must be closed so that only the previously retained grain will fall out and not any of the others. This operation is also a highly reliable one. It was found, however, that the rate of deposing pieces of grain in a sequential operation, as it is carried out by a planter, is limited to some extent simply because a certain margin of safety is required for blowing the grains up and sufficiently high so that, with certainty, none of them will fall through while the brackets are open.
In view of the irregularity and shape inherent in seeds, in many instances, one does need a significant margin of safety here, which, of course, means that a certain time elapses until a another grain again becomes situated on top of the duct in the reclosed bracket structure and another period of time will elapse, during which the other pieces of grain are blown out again.